Flow force compensating spool valve and hydraulic valve, pneumatic valve, three-way control valve, and four-way control valve using the same

ABSTRACT

Disclosed is a flow force compensating spool valve having a flow force compensating protrusion ring at a supply channel of a sleeve on an outer circumference portion of a spool rod, and a hydraulic valve, a pneumatic valve, a three-way valve, and a four-way valve using the spool valve, in which the flow force can be compensated by a simple structure change of the spool without changing a structure of the sleeve.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a spool valve, and moreparticularly, to a spool valve structure which can compensate flow forceapplied to the spool in a sleeve by changing the shape of a spool rod.

[0003] 2. Description of the Background Art

[0004] A spool valve indicates a valve which opens and closes a channelby a spool which moves toward a shaft direction in a sleeve.

[0005]FIG. 1 is a cross-sectional view showing a structure of a generalspool valve in accordance with the conventional art.

[0006] As shown, the conventional spool valve comprises a supply channel11(11 a, 11 b); a sleeve 10 having a feedback channel 12; and a spool 20having a plurality of spool lands 21 connected to one another as a unitby a spool rod 22. The spool 20 reciprocates in the sleeve 10 toward theshaft direction, thereby opening and closing the channels 11 and 12.

[0007] In the sleeve 10, one or two control channel 13(13 a, 13 b) isformed, which is called as a three-way control valve or a four-waycontrol valve according to the number of entire channels.

[0008] Herein, a flow of fluid which passes the spool valve will beexplained.

[0009] The fluid supplied through the supply channel 11 passes ametering orifice formed by a narrow space between an end portion of thesupply channel 11 and the spool land 21, thereby forming a fast flow.The fast flow is reflected by the spool rod 22 and then flows outthrough the control channel 13 or the feedback channel 12.

[0010] A size of a flow force applied to the spool 20 by the fluid isequal to that of a force by a pressure applied to a wall of the spoolland 21, and a direction of the flow force is opposite to that which thespool moves, that is, a direction which the metering orifice is closed.

[0011] The flow force will be expressed as follows by forces applied toeach part A, B, C, D, and E of the spool valve shown in FIG. 1

F _(flow force) =−F _(A) +F _(C) −F _(D) +F _(E)

[0012] When the flow force becomes large, a force required to move thespool of the valve also becomes great, so that a size of the entirevalve or a capacity of a driving motor has to be increased.

[0013] Accordingly, many methods for reducing or perishing the flowforce of a steady state have been proposed. However, only some parts ofthe methods were successful and the other parts were impractical.

[0014] In the American patent of a U.S. Pat. No. 4,220,178, a method forchanging a shape of the spool rod (a shank of the spool) of a hydrauliccontrol valve is proposed to change an exchange of a movement amountbetween the spool and a high pressure fluid so that many kinds ofdynamic forces applied to the spool be balanced one another.

[0015] The shank is formed to have an angle smaller than an inflow anglein order to remove the fast flow which can be generated at the spool.

[0016] However, said method accompanies one disadvantage that a maximumdiameter of the spool land is increased when compared with a structureof the conventional spool and has a problem that a shape of an exit rampis not easily and precisely fabricated.

[0017] Also, in the American patent of a U.S. Pat. No. 5,944,042, amethod for compensating the flow force by using a re-circulation land isproposed.

[0018] A hydrostatic bearing is formed in the sleeve and a groove isformed in the spool land to compensate the flow force by a turbulencegenerated by the structure.

[0019] However, said method requires a structure change of the sleeveitself, so that a fabricating cost is excessively increased and aprecise fabrication is impossible.

[0020] Also, in the American patent of a U.S. Pat. No. 3,123,335, amethod for compensating the flow force by forming a notch at the spoolland is proposed. However, said method requires a structure change ofthe sleeve itself, thereby excessively increasing a fabricating cost andnot being able to fabricate accurately.

SUMMARY OF THE INVENTION

[0021] Therefore, an object of the present invention is to provide aspool valve which can compensate a flow force by simply changing thestructure of a spool without changing a structure of a sleeve itself.

[0022] To achieve these and other advantages and in accordance with thepurpose of the present invention, as embodied and broadly describedherein, there is provided a spool valve comprising: a sleeve having asupply channel and a feedback channel, a spool having a plurality ofspool lands connected to one another by a spool rod, wherein thechannels are opened and closed by the spool which reciprocates in thesleeve toward the shaft direction, and a flow force compensatingprotrusion ring formed at the supply channel on the outer circumferenceportion of the spool rod.

[0023] The foregoing and other objects, features, aspects and advantagesof the present invention will become more apparent from the followingdetailed description of the present invention when taken in conjunctionwith the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings, which are included to provide afurther understanding of the invention and are incorporated in andconstitute a part of this specification, illustrate embodiments of theinvention and together with the description serve to explain theprinciples of the invention.

[0025] In the drawings:

[0026]FIG. 1 is a cross-sectional view showing a structure of a generalspool valve in accordance with the conventional art;

[0027] FIGS. 2 to 5 show structures of a spool valve according to thepresent invention;

[0028]FIG. 2 is a longitudinal sectional view showing a state that aleft supply channel is opened;

[0029]FIG. 3 is a longitudinal sectional view showing a state that aright supply channel is opened;

[0030]FIG. 4 is a perspective view showing a structure of the spool; and

[0031]FIG. 5 is a longitudinal sectional view showing another preferredembodiment of the present invention.

[0032]FIG. 6 is a longitudinal sectional view showing a chamfer formedat the flow force compensating protrusion ring.

[0033]FIG. 7 is a longitudinal sectional view showing a groove formed atthe flow force compensating protrusion ring.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0034] Reference will now be made in detail to the preferred embodimentsof the present invention, examples of which are illustrated in theaccompanying drawings.

[0035] In the spool valve, the flow force compensating protrusion ringcan be formed at the inner side surface of the spool land as a unit, orcan be formed separately from the inner side surface of the spool landwith a predetermined interval.

[0036] Also, the flow force compensating protrusion ring preferably hasa sectional surface of a shaft direction with a square shape.

[0037] Also, it is possible to form a chamfer at the end portion of theflow force compensating protrusion ring, and to form a groove at thesupply channel of the flow force compensating protrusion ring.

[0038] In the present invention, as another means for accomplishing saidpurposes, a hydraulic valve and a pneumatic valve using the spool valveare proposed.

[0039] Furthermore, in the present invention, as still another means foraccomplishing said purposes, a three-way valve which uses the spoolvalve and has a control channel, and a four-way valve having two controlchannels are proposed.

[0040] Hereinafter, a preferred embodiment of the present invention willbe explained with reference to the attached drawings.

[0041] FIGS. 2 to 5 show structures of a spool valve according to thepresent invention, in which FIG. 2 is a longitudinal sectional viewshowing a state that a left supply channel is opened, FIG. 3 is alongitudinal sectional view showing a state that a right supply channelis opened, FIG. 4 is a perspective view showing a structure of thespool, and FIG. 5 is a longitudinal sectional view showing anotherpreferred embodiment of the present invention.

[0042] As shown, the spool valve according to the present inventioncomprises: a sleeve 10 having a supply channel 11(11 a, 11 b) and afeedback channel 12; and a spool 100 having a plurality of spool lands21 connected to one another by a spool rod 22. The spool valve foropening and closing the channels 11 and 12 by the spool 100 whichreciprocates in the sleeve 10 toward the shaft direction has the sameconstruction with the conventional art.

[0043] However, the flow force compensating protrusion ring 30 is formedat the supply channel 11 on the outer circumstance portion of the spoolrod 22.

[0044] Herein, a flow of fluid which passes the spool valve will beexplained.

[0045] As shown in FIG. 2, when the left supply channel is opened, thefluid supplied through the supply channel 11 a passes a metering orificeformed at a narrow space between an end portion of the supply channel 11a and the spool land 21, thereby forming a fast flow. The fast flow doesnot collide with the spool rod 22 directly, but collides with a curvedsurface b of the flow force compensating protrusion ring 30 to bereflected and flows out through the control channel 13 a.

[0046] Accordingly, flow is generated only at the wall a1 of the spoolland not at the wall a2 of the flow force compensating protrusion ring.

[0047] Also, since the fluid reflected by the flow force compensatingprotrusion ring 30 is directly exhausted through the control channel 13a, the flow is not generated at the peripheral portion of the walls c1and c2 of the spool land, either.

[0048] Accordingly, a size of the force applied to the wall a2 of thespool land is increased as that applied to the wall c2 of the spoolland, so that a size of the flow force applied to the spool 100 isentirely decreased.

[0049] Also, as shown in FIG. 3, when the right supply channel 11 b isopened, the same effect can be anticipated.

[0050] That is, the fluid supplied through the supply channel 11 bpasses a metering orifice formed by a narrow space between the endportion of the supply channel 11 b and the spool land 21, therebyforming a fast flow. The fast flow does not collide with the spool rod22 directly, but collides with a curved surface f of the flow forcecompensating protrusion ring 30 to be reflected and flows out throughthe control channel 13 b.

[0051] Accordingly, the flow is generated only at the wall e1 of thespool land not at the wall e2 of the flow force compensating protrusionring.

[0052] Also, since the fluid reflected by the flow force compensatingprotrusion ring 30 is directly exhausted through the control channel 13b, the flow is not generated at the peripheral portion of the walls d1and d2 of the spool land, either.

[0053] Accordingly, a size of the force applied to the wall e2 of thespool land is increased as that applied to the wall d2 of the spoolland, so that a size of the flow force applied to the spool 100 isentirely decreased.

[0054] A size of the flow force applied to the spool valve according tothe present invention is expressed as the following equation.

F _(flow force) =−F _(a1) −F _(a2) +F _(c1) +F _(c2) −F _(d1) −F _(d2)+F _(e1) +F _(e2)

[0055] Herein, when the left supply channel is opened, F_(a2) and F_(c2)can be offset each other since the size of the force is equal and codesare opposite. Also, when the right supply channel is opened, F_(d2) andF_(e2) can be offset each other since the size of the force is equal andthe directions are opposite to each other.

[0056] Accordingly, when compared with the conventional one, the flowforce applied to the spool valve according to the present invention isdecreased as a force by a pressure applied to the wall a2 of the flowforce compensating protrusion ring when the left supply channel 11 a isopened. Also, when the right supply channel 11 b is opened, the flowforce applied to the spool valve according to the present invention isdecreased as a force by a pressure applied to the wall e2 of the flowforce compensating protrusion ring.

[0057] To realize the present invention, several embodiments can beproposed.

[0058] That is, as shown in FIGS. 2 and 3, the flow force compensatingprotrusion ring 30 can be formed on the inner side surface of the spoolland 21, or can be formed at the inner side surface of the spool land 21with a predetermined gap therebetween.

[0059] Also, since the walls a2 and e2 of the protrusion ring have to beformed to compensate the flow force, the flow force compensatingprotrusion ring 30 preferably has a square-shaped sectional surface inthe shaft direction.

[0060] Also, the sectional surfaces (‘A’ in FIG. 3) of the spool land21, the protrusion ring 30, and the spool rod 22 have only to form astep-type structure for the flow force compensation in order tocompensate the flow force. Therefore, in accordance with modifiedexamples a chamfer 35 can be formed at the end portion of the flow forcecompensating protrusion ring 30 as shown in FIG. 6 or a groove 40 can beformed at the surfaces b and f of the supply channel 11 of the flowforce compensating protrusion ring 30 as shown in FIG. 7.

[0061] The structure of the spool valve according to the presentinvention can be all applied to the hydraulic valve and the pneumaticvalve, and can be all applied to the three-way control valve and thefour-way control valve having one or two control channels.

[0062] The present invention provides the spool valve which cancompensate the flow force by a simple structure change of the spoolwithout requiring a structure change of the sleeve itself.

[0063] As the present invention may be embodied in several forms withoutdeparting from the spirit or essential characteristics thereof, itshould also be understood that the above-described embodiments are notlimited by any of the details of the foregoing description, unlessotherwise specified, but rather should be construed broadly within itsspirit and scope as defined in the appended claims, and therefore allchanges and modifications that fall within the metes and bounds of theclaims, or equivalence of such metes and bounds are therefore intendedto be embraced by the appended claims.

What is claimed is:
 1. A spool valve comprising: a sleeve having a supply channel and a feedback channel; a spool having a plurality of spool lands connected to one another by a spool rod, wherein the channels are opened and closed by the spool which reciprocates in the sleeve toward the shaft direction; and a flow force compensating protrusion ring formed at the supply channel on the outer circumference portion of the spool rod.
 2. The spool valve of claim 1, wherein the flow force compensating protrusion ring is formed on the inner side surface of the spool land.
 3. The spool valve of claim 1, wherein the flow force compensating protrusion ring is formed at the inner side surface of the spool land with a predetermined gap therebetween.
 4. The spool valve of claim 1, wherein the flow force compensating protrusion ring preferably has a square-shaped sectional surface in the shaft direction.
 5. The spool valve of claim 4, wherein a chamfer is formed at the end portion of the flow force compensating protrusion ring.
 6. The spool valve of claim 4, wherein a groove is formed at the supply channel of the flow force compensating protrusion ring.
 7. A hydraulic valve using the spool valve of one of claims 1 through
 6. 8. A pneumatic valve using the spool valve of one of claims 1 through
 6. 9. A three-way control valve using the spool valve of one of claims 1 through 6, wherein the sleeve is provided with a control channel.
 10. A four-way control valve using the spool valve of one of claims 1 through 6, wherein the sleeve is provided with two control channels. 